1. Field of the Invention
The present invention relates to thin-film type magnetic recording media of excellent short wavelength or high-frequency recording characteristics.
2. Prior Art
There has been an increasing tendency for magnetic recording and reproducing apparatus toward recording and reproducing information at higher and higher densities, so that there has been a strong demand for magnetic recording media of excellent short wavelength or high-frequency information recording capability. Conventional magnetic recording media are fabricated in general by applying magnetic powder over a substrate made of high-molecular compounds or nonmagnetic material (and will be referred to as "the coated type" hereinafter in this specification). In order to improve their short wavelength or high-frequency information recording capability, their coercive force and saturation magnetization must be increased, and the magnetic film or layer must be reduced in thickness. However, there are limits to the improvement of the conventional "coated type" magnetic recording medium for better short wavelength or high-frequency information capability, so that a great deal of research-and-development work has been made in order to fabricate thin-film type magnetic recording media. Thin-film type magnetic media can be fabricated by the vacuum evaporation, sputtering or electro- or chemical plating process and exhibit excellent short wavelength or high-frequency information recording capability. In general, thin magnetic films consist of Co; Co and Ni; Co and Cr; Co, Ni and Cr; Co and P; or Co, Ni and P.
Of the above-described three deposition processes, the sputtering process is not adapted for mass production because of slow sputtering or deposition rates. Furthermore, the thin magnetic film deposited by the sputtering process is not stable in maintaining its characteristics. On the other hand, the evaporation or deposition rate of the vacuum evaporation process is very fast and of the order of thousands of angstroms per second. In addition, stable thin magnetic films of high coercive force can be easily obtained when the supporting substrate is inclined at an angle to the incident beam of evaporating material. In this case, it is well known that the higher the oxygen content in the deposited thin film, the higher the coercive force H.sub.c becomes and that the larger the angle of vapor incidence, the higher the content of oxygen in the deposited thin film becomes. However, an increase in the angle of vapor incidence results in a remarkable decrease in the deposition rate.